State the law of conservation of linear momentum for a system of particles.

(N/A) The law of conservation of linear momentum states that if the net external force acting on a system of particles is zero,then the total linear momentum of the system remains constant.
Mathematically,if $\vec{F}_{ext} = 0$,then $\frac{d\vec{P}}{dt} = 0$,which implies $\vec{P} = \text{constant}$.
Here,$\vec{P} = \sum \vec{p}_i$ is the total linear momentum of the system.